scholarly journals Modeling and Analysis of a Piezoelectric Energy Harvester with Varying Cross-Sectional Area

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Maiara Rosa ◽  
Carlos De Marqui Junior
Keyword(s):  
Experimental Verification ◽  
Power Output ◽  
Optimization Problems ◽  
Load Resistance ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Beam Shape ◽  
Piezoelectric Energy ◽  
Tip Mass

This paper reports on the modeling and on the experimental verification of electromechanically coupled beams with varying cross-sectional area for piezoelectric energy harvesting. The governing equations are formulated using the Rayleigh-Ritz method and Euler-Bernoulli assumptions. A load resistance is considered in the electrical domain for the estimate of the electric power output of each geometric configuration. The model is first verified against the analytical results for a rectangular bimorph with tip mass reported in the literature. The experimental verification of the model is also reported for a tapered bimorph cantilever with tip mass. The effects of varying cross-sectional area and tip mass on the electromechanical behavior of piezoelectric energy harvesters are also discussed. An issue related to the estimation of the optimal load resistance (that gives the maximum power output) on beam shape optimization problems is also discussed.

Maximum Power From Fluid Flow: Results From the First and Second Laws of Thermodynamics

2012 ◽  
Author(s):  
German Amador Diaz ◽  
John Turizo Santos ◽  
Elkin Hernandez ◽  
Ricardo Vasquez Padilla ◽  
Lesme Corredor
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Power Output ◽  
Power Plants ◽  
Cross Sectional Area ◽  
Maximum Power ◽  
Sectional Area ◽  
Cross Sectional ◽  
Maximum Power Output ◽  
Piston Cylinder

The heat transfer principle of power maximization in power plants with heat transfer irreversibilities was cleverly extended by Bejan [1] to fluid flow, by obtaining that the energy conversion efficiency at maximum power is ηmax = 1/2(1 − P2/P1). This result is analog to the efficiency at maximum power for power plants, ηmax = 1 − (T2/T1)1/2 which was deduced by Curzon and Ahlborn [2]. In this paper, the analysis to obtain maximum power output delivered from a piston between two pressure reservoir across linear flow resistance is generalized by considering the piston cylinder friction, by obtaining relations of maximum power output and optimal speed of the piston in terms of first law efficiency. Expressions to relate the power output, cross sectional area of the chamber and first law efficiency, were deduced in order to evaluate the influence of the overall size constraints and fluid regime in the performance of the piston cylinder system. Flow in circular ducts and developed laminar flow between parallel plates, are considered to demonstrate that when two pressure reservoirs oriented in counterflow, with different and arbitrary cross sectional area, must have the same area in order to maximize the power output of the system. These results introduce some modifications to the results obtained by Bejan [1] and Chen [3]. This paper extends the Bejan and Chen’s work by estimating under turbulent regime the lost available work rate associated with the degree of irreversibilities caused by the flow resistances of the system. This analysis is equivalent to evaluate the irreversibilities in an endoirreversible Carnot heat engine model caused by the heat resistance loss between the engine and its surrounding heat reservoirs. This paper concludes with an application to illustrate the practical applications by estimating the lost available work of an actual steady-flow turbine and the layout pipes upstream and downstream of the same device.

Design Innovation Size and Shape Optimization of a 1.0mm Multifunctional Forceps-Scissors Surgical Instrument

2008 ◽  
Vol 2 (1) ◽  
Author(s):  
Milton E. Aguirre ◽  
Mary Frecker
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Shape Optimization ◽  
Optimization Problems ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Element Analysis ◽  
Cross Sectional ◽  
Size And Shape ◽  
The Cross

A size and shape optimization routine is developed for a 1.0mm diameter multifunctional instrument for minimally invasive surgery. The instrument is a compliant mechanism capable of both grasping and cutting. Multifunctional instruments are expected to be beneficial in the operating room because of their ability to perform multiple surgical tasks, thereby decreasing the total number of instrument exchanges in a single procedure. With fewer instrument exchanges, the risk of inadvertent tissue trauma as well as overall surgical time and costs are reduced. The focus of this paper is to investigate the performance effects of allowing the cross-sectional area along the length of the device to vary. This investigation is accomplished by defining various cross-sectional segments in terms of parametric variables and optimizing the dimensions of the instrument to provide a sufficient opening of the forceps jaws while maintaining adequate cutting and grasping forces. Two optimization problems are considered. First, all parametric segments are set equal to one another to achieve size optimization. Second, each segment is allowed to vary independently, thereby achieving shape optimization. Large deformation finite element analysis and optimization are conducted using ANSYS®. Finally, prototypes are fabricated using wire EMD and experiments are conducted to evaluate the instrument performance. As a result of allowing the cross-sectional area to vary, i.e., conducting shape optimization, the forceps and scissors blocked forces increased by as much as 83.2% and 87%, respectively. During prototype evaluations, it is found that the finite element analysis predictions were within 10% of the measured tool performance. Therefore, for this application, it is concluded that performing shape optimization does significantly influence the performance of the instrument.

Convective Heat Transfer and Contact Resistances Effects on Performance of Conventional and Composite Thermoelectric Devices

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
B. V. K. Reddy ◽  
Matthew Barry ◽  
John Li ◽  
Minking K. Chyu
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Conversion Efficiency ◽  
Power Output ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Transfer Coefficients ◽  
Cross Sectional ◽  
Heat Transfer Coefficients

The performance of Π shaped conventional and composite thermoelectric devices (TEDs) applied to waste heat recovery by taking the Fourier heat conduction, Joule heating, and the Peltier and Thomson effects in TE materials is investigated using analytical solutions. The TE legs built with semiconductor materials bonded onto a highly conductive interconnector material in a segmented fashion is treated as the composite TED, whereas the legs merely made from semiconductors is treated as the conventional TED. The top and bottom surfaces of TEDs are subjected to convective heat transfer conditions while the remaining surfaces exposed to ambient are kept adiabatic. The effects of contact resistances, convective heat transfer coefficients, and TE leg heights L on TEDs' performance are studied. An increase in electrical and/or thermal contact resistance and a decrease in heat transfer coefficients are resulted in a decrease in power output P0 and conversion efficiency η. Depending on the contact resistances and convective heat transfer loads, the optimum L where a maximum Po occurs is obtained typically in the range of 1–4 mm. For TE leg size greater than optimum L and TED operating under higher convective heat transfer conditions, the composite design exhibited better power output and lower conversion efficiency compared to conventional design. The effects of interconnector lengths and cross-sectional area on the composite TED's characteristics are also investigated. An increase in a length and a decrease in a cross-sectional area of the interconnector decreases the composite TED's performance. However, based on the increase of the interconnector's electrical resistance in relation to the device's total internal resistance, the composite TED exhibited both negligible and significant change behavior in P0.

The relationship between passive stiffness and muscle power output: Influence of muscle cross-sectional area normalization

2013 ◽  
Vol 49 (1) ◽  
pp. 69-75 ◽  
Author(s):  
Ty B. Palmer ◽  
Nathaniel D.M. Jenkins ◽  
Brennan J. Thompson ◽  
Douglas B. Smith ◽  
Joel T. Cramer
Keyword(s):  
Power Output ◽  
Muscle Power ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Passive Stiffness ◽  
Cross Sectional ◽  
Muscle Cross Sectional Area ◽  
The Relationship ◽  
Muscle Power Output

The emission of internal waves by vibrating cylinders

1969 ◽  
Vol 36 (4) ◽  
pp. 657-672 ◽  
Author(s):  
D. G. Hurley
Keyword(s):  
Internal Waves ◽  
Cross Sections ◽  
Power Output ◽  
Simple Expression ◽  
Cross Sectional Area ◽  
Rate Of Change ◽  
Body Of Revolution ◽  
Sectional Area ◽  
Cross Sectional ◽  
The Cross

The paper describes an investigation of the internal waves that are produced in a stratified fluid having constant Brunt—Väisälä frequency by a cylinder which executes small vibrations at a lower frequency. Explicit solutions are found for slender cylinders having arbitrary cross-sections. When the cross-sectional area of the cylinder varies with time it is found necessary in calculating the surface pressures and power output to take account of terms in the governing equations that are significant only at distances from the cylinder comparable to or larger than the scale height of the density variations. For this case a simple expression for the power output is obtained in terms of the rate of change of the cross-sectional area of the cylinder.When the vibrating cylinder is rigid its cross-sectional area is independent of time and then the expression for the power output is very similar to von Kármán's expression for the drag of a body of revolution in supersonic flow.In both the above cases it is found that one quarter of the power is radiated in each of the four directions that are inclined at a particular angle to the horizontal.

Pelvic Canal Narrowing Caused by Triple Pelvic Osteotomy in the Dog

1994 ◽  
Vol 07 (03) ◽  
pp. 110-113 ◽  
Author(s):  
D. L. Holmberg ◽  
M. B. Hurtig ◽  
H. R. Sukhiani
Keyword(s):  
Postoperative Complications ◽  
Pelvic Osteotomy ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Canal Width ◽  
Operative Complications ◽  
Post Operative Complications

SummaryDuring a triple pelvic osteotomy, rotation of the free acetabular segment causes the pubic remnant on the acetabulum to rotate into the pelvic canal. The resulting narrowing may cause complications by impingement on the organs within the pelvic canal. Triple pelvic osteotomies were performed on ten cadaver pelves with pubic remnants equal to 0, 25, and 50% of the hemi-pubic length and angles of acetabular rotation of 20, 30, and 40 degrees. All combinations of pubic remnant lengths and angles of acetabular rotation caused a significant reduction in pelvic canal-width and cross-sectional area, when compared to the inact pelvis. Zero, 25, and 50% pubic remnants result in 15, 35, and 50% reductions in pelvic canal width respectively. Overrotation of the acetabulum should be avoided and the pubic remnant on the acetabular segment should be minimized to reduce postoperative complications due to pelvic canal narrowing.When performing triple pelvic osteotomies, the length of the pubic remnant on the acetabular segment and the angle of acetabular rotation both significantly narrow the pelvic canal. To reduce post-operative complications, due to narrowing of the pelvic canal, overrotation of the acetabulum should be avoided and the length of the pubic remnant should be minimized.

DETERMINATION OF THE FUNCTION OF THE ROD’S CROSS-SECTIONAL AREA USING VIBRATION EIGENFREQUENCIES

2020 ◽  
Vol 0 (4) ◽  
pp. 19-24
Author(s):  
I.M. UTYASHEV ◽  
◽  
A.A. AITBAEVA ◽  
A.A. YULMUKHAMETOV ◽  
◽  
...  
Keyword(s):  
Cross Sectional Area ◽  
Variable Cross ◽  
Sectional Area ◽  
Longitudinal Vibrations ◽  
Cross Sectional ◽  
Method Error ◽  
Various Boundary Conditions ◽  
Elastic Fixation ◽  
Crosssectional Area

The paper presents solutions to the direct and inverse problems on longitudinal vibrations of a rod with a variable cross-sectional area. The law of variation of the cross-sectional area is modeled as an exponential function of a polynomial of degree n . The method for reconstructing this function is based on representing the fundamental system of solutions of the direct problem in the form of a Maclaurin series in the variables x and λ. Examples of solutions for various section functions and various boundary conditions are given. It is shown that to recover n unknown coefficients of a polynomial, n eigenvalues are required, and the solution is dual. An unambiguous solution was obtained only for the case of elastic fixation at one of the rod’s ends. The numerical estimation of the method error was made using input data noise. It is shown that the error in finding the variable crosssectional area is less than 1% with the error in the eigenvalues of longitudinal vibrations not exceeding 0.0001.

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